In-Situ Adsorbate Formation for Plasma Etch Process
A method of processing a substrate that includes: flowing dioxygen (O2) and an adsorbate precursor into a plasma processing chamber that is configured to hold the substrate including an organic layer and a patterned etch mask; sustaining an oxygen-rich plasma while flowing the O2 and the adsorbate precursor, oxygen species from the O2 and the adsorbate precursor reacting under the oxygen-rich plasma to form an adsorbate; and exposing the substrate to the oxygen-rich plasma to form a recess in the organic layer, where the adsorbate forms a sidewall passivation layer in the recess.
The present invention relates generally to methods of processing a substrate, and, in particular embodiments, to neutral adsorption enhancement via in-situ adsorbate formation.
BACKGROUNDGenerally, a semiconductor device, such as an integrated circuit (IC) is fabricated by sequentially depositing and patterning layers of dielectric, conductive, and semiconductor materials over a substrate to form a network of electronic components and interconnect elements (e.g., transistors, resistors, capacitors, metal lines, contacts, and vias) integrated in a monolithic structure. Many of the processing steps used to form the constituent structures of semiconductor devices are performed using plasma processes.
The semiconductor industry has repeatedly reduced the minimum feature sizes in semiconductor devices to a few nanometers to increase the packing density of components. Accordingly, the semiconductor industry increasingly demands plasma processing technology to provide processes for patterning features with accuracy, precision, and profile control, often at atomic scale dimensions. Meeting this challenge along with the uniformity and repeatability needed for high volume IC manufacturing requires further innovations of plasma processing technology.
SUMMARYIn accordance with an embodiment of the present invention, a method of processing a substrate that includes: flowing dioxygen (O2) and an adsorbate precursor into a plasma processing chamber that is configured to hold the substrate including an organic layer and a patterned etch mask; sustaining an oxygen-rich plasma while flowing the O2 and the adsorbate precursor, oxygen species from the O2 and the adsorbate precursor reacting under the oxygen-rich plasma to form an adsorbate; and exposing the substrate to the oxygen-rich plasma to form a recess in the organic layer, where the adsorbate forms a sidewall passivation layer in the recess.
In accordance with an embodiment of the present invention, a method of processing a substrate that includes: flowing a P-containing adsorbate precursor and a halogen-free gas including dioxygen (O2) into a plasma processing chamber that is configured to hold the substrate including an organic layer and a patterned etch mask, where a ratio of a flow rate of O2 to a flow rate of the P-containing adsorbate precursor is at least 1:1; sustaining an oxygen-rich plasma while flowing the P-containing adsorbate precursor and the halogen-free gas, oxygen species from the O2 and the P-containing adsorbate precursor reacting under the oxygen-rich plasma to form a P-containing adsorbate; and exposing the substrate to the oxygen-rich plasma to form a recess in the organic layer, where the P-containing adsorbate forms a sidewall passivation layer in the recess.
In accordance with an embodiment of the present invention, a method of processing a substrate that includes: loading the substrate in a plasma processing chamber, the substrate including a dielectric layer, an amorphous carbon layer (ACL) and a patterned etch mask; flowing dioxygen (O2), a P-containing adsorbate precursor, and a hydrogen-containing gas into the plasma processing chamber; sustaining a halogen-free plasma in the plasma processing chamber, where a P-containing adsorbate and H2O are formed under the halogen-free plasma; exposing the substrate to the halogen-free plasma to form a recess in the ACL; and exposing the substrate to a halogen-containing plasma to extend the recess into the dielectric layer.
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
This application relates to fabrication of semiconductor devices, for example, integrated circuits comprising semiconductor devices, and more particularly to high capacity three-dimensional (3D) memory devices, such as a 3D-NAND (or vertical-NAND), 3D-NOR, or dynamic random access memory (DRAM) device. The fabrication of such devices may generally require forming conformal, high aspect ratio (HAR) features (e.g., a contact hole) of a circuit element. Features with aspect ratio (ratio of height of the feature to the width of the feature) higher than 20:1 are generally considered to be high aspect ratio features, and in some cases fabricating a higher aspect ratio such as 100:1 may be desired for advanced 3D semiconductor devices. In such applications, HAR features may be formed in a dielectric layer (e.g., silicon oxide, silicon nitride, or oxide/nitride layer stack) by a highly anisotropic plasma etch process with high fidelity. To enable ideal etch performance for HAR features, an etch mask, for example, amorphous carbon layer (ACL), must with a HAR also be prepared prior to etching the dielectric layer. This etch process for the etch mask (e.g., ACL) may be based on O2-sulfur chemistry to achieve highly vertical etch profile and high etch rate with minimal irregularities (e.g., contact edge roughness, line edge roughness, and/or line width roughness). However, the use of sulfur in the etch process, although helpful in passivating sidewalls to minimize lateral etching, can cause acidic contamination during the process. Therefore, a new etch method that does not require sulfur may be desired for patterning an etch mask with high aspect ratio (HAR) features. Embodiments of the present application disclose methods of fabricating HAR features by a plasma etch process based on a combination of in-situ adsorbate formation and sidewall passivation by the formed adsorbates.
In various embodiments, phosphorous (P)-containing adsorbates such as H3PO4 may be formed in a plasma processing chamber during a plasma etch process, and they may advantageously provide sidewall passivation to enable a HAR feature with minimized line wiggling, bowing, and/or twisting. The inventors of this application identified that P-containing adsorbates may exhibit a higher energy of adsorption on a carbon-containing surface than H2O. H2O may be used as another effective adsorbate for sidewall passivation while etching an organic layer, but generally requires low-temperature conditions (e.g., temperature below 0° C.), which may be costly. Using the P-containing adsorbates in place of, or in addition to, H2O, it may be possible to eliminate the need of such low temperature conditions. In certain embodiments, other types of adsorbates comprising other elements such as B, S, Si, and/or N may also be used.
In the following, an exemplary plasma etch process to form a high aspect ratio (HAR) feature is described in accordance with various embodiments referring to
In one or more embodiments, the substrate 100 may be a silicon wafer, or a silicon-on-insulator (SOI) wafer. In certain embodiments, the substrate 100 may comprise a silicon germanium wafer, silicon carbide wafer, gallium arsenide wafer, gallium nitride wafer and other compound semiconductors. In other embodiments, the substrate comprises heterogeneous layers such as silicon germanium on silicon, gallium nitride on silicon, silicon carbon on silicon, as well layers of silicon on a silicon or SOI substrate.
In various embodiments, the substrate 100 is a part of, or include, a semiconductor device, and may have undergone a number of steps of processing following, for example, a conventional process. For example, the semiconductor structure may comprise a substrate 100 in which various device regions are formed. At this stage, the substrate 100 may include isolation regions such as shallow trench isolation (STI) regions as well as other regions formed therein.
The underlying layer 110 may be formed over the substrate 100. In various embodiments, the underlying layer 110 is a target layer that is to be patterned by a subsequent plasma etch process after patterning the material layer 120. In certain embodiments, the feature being etched into the underlying layer 110 may be a contact hole, slit, or other suitable structures comprising a recess. In various embodiments, the underlying layer 110 may comprise a dielectric material. In certain embodiments, the underlying layer 110 may be a silicon oxide layer. In alternate embodiments, the underlying layer 110 may comprise silicon nitride, silicon oxynitride, or an O/N/O/N layer stack (stacked layers of oxide and nitride). The underlying layer 110 may be deposited using an appropriate technique such as vapor deposition including chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), as well as other plasma processes such as plasma enhanced CVD (PECVD) and other processes. In one embodiment, the underlying layer 110 has a thickness between 1 μm and 10 μm.
Still referring to
Further illustrated in
Although not specifically illustrated in
Fabricating the HAR feature in the material layer 120 may be performed by a plasma etch process based on O2 etch chemistry. In various embodiments, an oxygen-containing gas such as dioxygen (O2) may be used as a primary etch gas. In certain embodiments, the plasma for the plasma etch process may be an oxygen-rich and halogen-free plasma. In one or more embodiments, the plasma may be a fluorine-free plasma. In addition, an adsorbate precursor may be included in a process gas such that, under a plasma condition, an adsorbate may be formed in a plasma processing chamber. In various embodiments, the adsorbate may comprise phosphorous. In one or more embodiments, the adsorbate formed in the plasma chamber may comprise phosphoric acid (H3PO4). The inventors of this application identified that H3PO4 may be an effective adsorbate that provides sidewall passivation. However, H3PO4 is nonvolatile and it is therefore impractical to directly deliver it in a gas phase to the plasma processing chamber. In various embodiments, the methods deliver an adsorbate precursor to enable in-situ formation of the adsorbate in the plasma processing chamber. The in-situ formation of adsorbate such as H3PO4 can overcome the issue of nonvolatility. Accordingly, the adsorbate precursor may comprise phosphorous. Examples of the P-containing adsorbate precursor include PH3 and PCl3.
In other embodiments, the adsorbate may comprise other elements such as B, S, Si, and/or N, and the adsorbate precursor may accordingly comprise these elements. In certain embodiment, the adsorbate precursor may comprise B2H6, SixHy, H2S, or NH3. Accordingly, the adsorbate formed in the plasma chamber may comprise boric acid, silicic acid, sulfuric acid, nitric acid, or similar acidic molecules comprising B, S, Si, and/or N. These acidic molecules may be exposed to behave similarly to phosphoric acid (H3PO4) and thereby function as an effective adsorbate for sidewall passivation.
In one or more embodiments, in addition to the adsorbate precursor, the process gas may further comprise a hydrogen-containing gas such as water (H2O), dihydrogen (H2), a hydrocarbon (e.g., CH4), or hydrogen peroxide (H2O2). The hydrogen-containing as may act as another adsorbate precursor and/or co-adsorbate. In certain embodiments, other gases such as a noble gas and/or a balancing agent may also be added.
The addition of the hydrogen-containing gas in the process gas may also benefit the etch rate, which may in turn enable a shorter process time compared to conventional HAR etch methods. Although not wishing to be limited by any theory, the addition of the hydrogen-containing gas (e.g., H2) may advantageously enhance the dissociation of O2 in the plasma and increase the number of reactive species such as oxygen radical.
Further, in various embodiments, adsorbates may comprise neutral species in a plasma system and effective in surface modification/activation during a plasma etch process such as reactive ion etching (RIE). By increasing the amount of neutrals in the plasma, the methods may advantageously enhance the etch rate. Further, the neutral adsorbate may also provide sidewall passivation that improve the anisotropy of the plasma etch process.
In
In various embodiments, process parameters may be selected to optimize the characteristics of the high aspect ratio (HAR) feature considering various factors comprising etch rate, selectivity to the etch mask (e.g., the patterned mask layer 130), sidewall passivation in the HAR feature, and good critical dimension uniformity (CDU) among others. The process parameters may comprise gas selection, gas flow rates, pressure, temperature, process time, and plasma conditions such as source power, bias power, RF pulsing conditions.
In certain embodiments, a ratio of a flow rate of the oxygen-containing gas (e.g., O2) to a flow rate of the adsorbate precursor (e.g., PH3) may be between 100:1 and 1:1. In one or more embodiments, the ratio of the flow rate may be between 20:1 and 10:1. In various embodiments, the gas composition and their flow rates may be selected to obtain an oxygen-rich plasma for the plasma etch process, which can be generally used for etching carbon materials such as ACL. In the oxygen-rich plasma, reactive species are predominantly oxygen-containing species, where the amount of oxygen-absent species are not greater than that of oxygen-containing species. The inventors of this application identified that the particular combination of O2 and an adsorbate precursor (e.g., PH3) can be critical in sufficiently providing the effect of adsorbates during etching carbon materials such as ACL.
In certain embodiments, the plasma may be an oxygen-rich, halogen-free plasma. In another embodiment, the plasma may be formed from a halogen-free gas comprising dioxygen (O2), while the adsorbate precursor may be the only halogen-containing gas among the gases flowed into the plasma processing chamber. Avoiding halogen for the methods of etching carbon materials such as ACL may be particularly advantageous for fabricating HAR structures, for example, for 3D-NAND devices. This is because such a fabrication process typically involves (1) ACL patterning, followed by (2) a dielectric etch using the patterned ACL as an etch mask, and halogen-free etch chemistry in the ACL patterning can provide better etch selectivity to the etch mask for ACL patterning (e.g., the patterned mask layer 130 in
In various embodiments, the substrate temperature may be kept at room temperature during the plasma etch process.
The recesses 135 may be in any shapes and structures, including a contact hole, slit, or other suitable structures comprising a recess useful for semiconductor device fabrication. In various embodiments, the features defined by the recesses 135 has a critical dimension (CD) of 200 nm or less. In certain embodiments, the CD may be between 50 nm and 200 nm. For example, the feature may comprise a slit with a CD of about 150 nm. In alternate embodiments, the recesses 135 may comprise a hole that has a top opening with a diameter of 80 nm or less.
The HAR feature in the material layer 120 prepared in
As illustrated in
In certain embodiments, the subsequent plasma etch process may be advantageously performed as a continuous process with a process time of 60 min or less to form a high aspect ratio (HAR) feature in the underlying layer 110 with an aspect ratio of 20:1 or higher. Further processing may follow conventional processing, for example, by removing any remaining portion of the material layer 120.
In various embodiments, the plasma etch process for the material layer 120 (
In
In
The inventors of this disclosure identified a P-containing adsorbate may be advantageous in providing sidewall passivation without low-temperature conditions through quasi-continuum density functional theory (QC-DFT) simulations. Two modes of adsorption are compared: H2O adsorption on C—OH surface (
Further simulations were conducted to calculate formation energies for an example P-adsorbate, PH2OH. The calculate energy of in-situ formation is −7.2542 eV when starting from PH3 and O(1D) (
In
In
In
The plasma system 800 is by example only. In various alternative embodiments, the plasma system 800 may be configured to sustain inductively coupled plasma (ICP) with RF source power coupled to a planar coil over a top dielectric cover, or capacitively coupled plasma (CCP) sustained using a disc-shaped top electrode in the plasma processing chamber 850. Alternately, other suitable configurations such as electron cyclotron resonance (ECR) plasma sources and/or a helical resonator may be used. The RF-bias power source 570 may be used to supply continuous wave (CW) or pulsed RF power to sustain the plasma. Gas inlets and outlets may be coupled to sidewalls of the plasma processing chamber, and pulsed RF power sources and pulsed DC power sources may also be used in some embodiments. In various embodiments, the RF power, chamber pressure, substrate temperature, gas flow rates and other plasma process parameters may be selected in accordance with the respective process recipe.
Although not described herein, embodiments of the present invention may be also applied to remote plasma systems as well as batch systems. For example, the substrate holder may be able to support a plurality of wafers that are spun around a central axis as they pass through different plasma zones.
Example embodiments of the invention are summarized here. Other embodiments can also be understood from the entirety of the specification as well as the claims filed herein.
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- Example 1. A method of processing a substrate that includes: flowing dioxygen (O2) and an adsorbate precursor into a plasma processing chamber that is configured to hold the substrate including an organic layer and a patterned etch mask; sustaining an oxygen-rich plasma while flowing the O2 and the adsorbate precursor, oxygen species from the O2 and the adsorbate precursor reacting under the oxygen-rich plasma to form an adsorbate; and exposing the substrate to the oxygen-rich plasma to form a recess in the organic layer, where the adsorbate forms a sidewall passivation layer in the recess.
- Example 2. The method of example 1, where the organic layer includes amorphous carbon layer (ACL).
- Example 3. The method of one of examples 1 or 2, where the adsorbate includes H3PO4, and where the adsorbate precursor includes phosphorous.
- Example 4. The method of one of examples 1 to 3, where the adsorbate precursor includes PH3 or PCl3.
- Example 5. The method of one of examples 1 to 4, where the adsorbate includes boron.
- Example 6. The method of one of examples 1 to 5, where the adsorbate includes silicon halide.
- Example 7. The method of one of examples 1 to 6, where the adsorbate includes sulfur.
- Example 8. The method of one of examples 1 to 7, where the adsorbate includes nitrogen.
- Example 9. The method of one of examples 1 to 8, further including flowing a H-containing gas.
- Example 10. The method of one of examples 1 to 9, where the H-containing gas includes water vapor (H2O), hydrogen peroxide (H2O2), dihydrogen (H2), or hydrogen bromide (HBr).
- Example 11. The method of one of examples 1 to 10, further including maintaining a substrate temperature above 0° C. while exposing the substrate to the oxygen-rich plasma.
- Example 12. A method of processing a substrate that includes: flowing a P-containing adsorbate precursor and a halogen-free gas including dioxygen (O2) into a plasma processing chamber that is configured to hold the substrate including an organic layer and a patterned etch mask, where a ratio of a flow rate of O2 to a flow rate of the P-containing adsorbate precursor is at least 1:1; sustaining an oxygen-rich plasma while flowing the P-containing adsorbate precursor and the halogen-free gas, oxygen species from the O2 and the P-containing adsorbate precursor reacting under the oxygen-rich plasma to form a P-containing adsorbate; and exposing the substrate to the oxygen-rich plasma to form a recess in the organic layer, where the P-containing adsorbate forms a sidewall passivation layer in the recess.
- Example 13. The method of example 12, further including flowing a noble gas into the plasma processing chamber.
- Example 14. The method of one of examples 12 or 13, where the oxygen-rich plasma is an inductively coupled plasma (ICP).
- Example 15. The method of one of examples 12 to 14, where the recess has an aspect ratio of at least 20:1.
- Example 16. The method of one of examples 12 to 15, further including flowing water vapor (H2O), hydrogen peroxide (H2O2), dihydrogen (H2), or hydrogen bromide (HBr).
- Example 17. A method of processing a substrate that includes: loading the substrate in a plasma processing chamber, the substrate including a dielectric layer, an amorphous carbon layer (ACL) and a patterned etch mask; flowing dioxygen (O2), a P-containing adsorbate precursor, and a hydrogen-containing gas into the plasma processing chamber; sustaining a halogen-free plasma in the plasma processing chamber, where a P-containing adsorbate and H2O are formed under the halogen-free plasma; exposing the substrate to the halogen-free plasma to form a recess in the ACL; and exposing the substrate to a halogen-containing plasma to extend the recess into the dielectric layer.
- Example 18. The method of example 17, where a portion of the recess in the dielectric layer has an aspect ratio of at least 20:1.
- Example 19. The method of one of examples 17 or 18, where the dielectric layer includes silicon oxide or silicon nitride.
- Example 20. The method of one of examples 17 to 19, where the recess defines a feature having a critical dimension between 50 nm and 200 nm.
While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments.
Claims
1. A method of processing a substrate, the method comprising:
- flowing dioxygen (O2) and an adsorbate precursor into a plasma processing chamber that is configured to hold the substrate comprising an organic layer and a patterned etch mask;
- sustaining an oxygen-rich plasma while flowing the O2 and the adsorbate precursor, oxygen species from the O2 and the adsorbate precursor reacting under the oxygen-rich plasma to form an adsorbate; and
- exposing the substrate to the oxygen-rich plasma to form a recess in the organic layer, wherein the adsorbate forms a sidewall passivation layer in the recess.
2. The method of claim 1, wherein the organic layer comprises amorphous carbon layer (ACL).
3. The method of claim 1, wherein the adsorbate comprises H3PO4, and wherein the adsorbate precursor comprises phosphorous.
4. The method of claim 3, wherein the adsorbate precursor comprises PH3 or PCl3.
5. The method of claim 1, wherein the adsorbate comprises boron.
6. The method of claim 1, wherein the adsorbate comprises silicon halide.
7. The method of claim 1, wherein the adsorbate comprises sulfur.
8. The method of claim 1, wherein the adsorbate comprises nitrogen.
9. The method of claim 1, further comprising flowing a H-containing gas.
10. The method of claim 9, wherein the H-containing gas comprises water vapor (H2O), hydrogen peroxide (H2O2), dihydrogen (H2), or hydrogen bromide (HBr).
11. The method of claim 1, further comprising maintaining a substrate temperature above 0° C. while exposing the substrate to the oxygen-rich plasma.
12. A method of processing a substrate, the method comprising:
- flowing a P-containing adsorbate precursor and a halogen-free gas comprising dioxygen (O2) into a plasma processing chamber that is configured to hold the substrate comprising an organic layer and a patterned etch mask, wherein a ratio of a flow rate of O2 to a flow rate of the P-containing adsorbate precursor is at least 1:1;
- sustaining an oxygen-rich plasma while flowing the P-containing adsorbate precursor and the halogen-free gas, oxygen species from the O2 and the P-containing adsorbate precursor reacting under the oxygen-rich plasma to form a P-containing adsorbate; and
- exposing the substrate to the oxygen-rich plasma to form a recess in the organic layer, wherein the P-containing adsorbate forms a sidewall passivation layer in the recess.
13. The method of claim 12, further comprising flowing a noble gas into the plasma processing chamber.
14. The method of claim 12, wherein the oxygen-rich plasma is an inductively coupled plasma (ICP).
15. The method of claim 12, wherein the recess has an aspect ratio of at least 20:1.
16. The method of claim 12, further comprising flowing water vapor (H2O), hydrogen peroxide (H2O2), dihydrogen (H2), or hydrogen bromide (HBr).
17. A method of processing a substrate, the method comprising:
- loading the substrate in a plasma processing chamber, the substrate comprising a dielectric layer, an amorphous carbon layer (ACL) and a patterned etch mask;
- flowing dioxygen (O2), a P-containing adsorbate precursor, and a hydrogen-containing gas into the plasma processing chamber;
- sustaining a halogen-free plasma in the plasma processing chamber, wherein a P-containing adsorbate and H2O are formed under the halogen-free plasma;
- exposing the substrate to the halogen-free plasma to form a recess in the ACL; and
- exposing the substrate to a halogen-containing plasma to extend the recess into the dielectric layer.
18. The method of claim 17, wherein a portion of the recess in the dielectric layer has an aspect ratio of at least 20:1.
19. The method of claim 17, wherein the dielectric layer comprises silicon oxide or silicon nitride.
20. The method of claim 17, wherein the recess defines a feature having a critical dimension between 50 nm and 200 nm.
Type: Application
Filed: Sep 30, 2022
Publication Date: Apr 4, 2024
Inventors: Du Zhang (Albany, NY), Yu-Hao Tsai (Albany, NY), Masahiko Yokoi (Miyagi), Yoshihide Kihara (Miyagi), Mingmei Wang (Albany, NY)
Application Number: 17/937,151